WO2005036741A1

WO2005036741A1 - Noise prevention coil circuit

Info

Publication number: WO2005036741A1
Application number: PCT/JP2004/015574
Authority: WO
Inventors: Hiroo Arikawa; Masaya Maruo
Original assignee: Soc Corporation
Priority date: 2003-10-14
Filing date: 2004-10-14
Publication date: 2005-04-21
Also published as: JPWO2005036741A1

Abstract

There is provided a noise prevention circuit to be connected between a communication input unit and a communication circuit. When the AC voltage of the high-frequency signal is E, the voltage between coil circuit terminals HS is V, the inner resistance of the load is r in the communication circuit, the ratio of the AC voltage E of the signal against the inter-terminal HS voltage for the input high-frequency signal is V/E <= 0.1, the impedance is small, and the high-frequency signal can flow to the load. The impedance is significantly increased for an abnormally intense noise, thereby preventing flow of the noise into the load.

Description

Description Noise prevention coil circuit Technical field

The present invention relates to a protection circuit for preventing external noise from flowing into a communication input section of an electronic device such as a communication device. Background art

Information communication is performed by passing high-frequency signals through a dedicated communication line or a commercial power supply AC voltage line, but the dedicated communication line may generate induced voltage noise due to lightning, In some cases, induced voltage noise due to lightning and surge voltage noise due to turning on and off electrical equipment with large power may flow.

As shown in Fig. 19, a conventional method for preventing noise in high-frequency circuits is to connect a constant voltage element such as a palister or arrester between the line (H) of the communication input and the ground, and connect a resistor R30 in series with the load. I do. When a large noise current flows through the resistor R30, the voltage generated at the resistor R30 increases the voltage applied to the constant-voltage element, allowing the constant-voltage element to function. By flowing the current to the ground and lowering the high voltage at the communication input, a large amount of noise flowing to the load is slightly reduced by the resistor R30. If a resistor with a large resistance value is connected, noise can be greatly reduced, but at the same time, a normal high-frequency signal is also greatly attenuated, so a large resistance value cannot be set.

In a low-frequency circuit having a relatively low signal frequency, a coil is connected instead of the resistor R30 in FIG. In order to prevent noise from flowing to the load with a coil, it is necessary to use a coil with a certain amount of inductance, so it can be used in low frequency circuits, but in high frequency circuits, it can be used in coils. The coil cannot be used because the impedance becomes large and the high frequency signal is greatly attenuated. Therefore, high-frequency circuits had the disadvantage that noise could not be sufficiently prevented by merely weakening the noise with a resistor. In information communication using high-frequency signals, this drawback is a major obstacle to the safety and reliability of communication devices and communication networks. Specifically, there were problems such as a large lightning surge or other noise that caused many communication devices in the area to break down, and that the communication network was cut off.

As a remedy, a circuit in which the coaxial cable is used as the primary side of the transformer and a resistor is connected between both ends of the secondary winding to absorb lightning noise induced in the coaxial cable for communication ( Japanese Patent Laid-Open No. 7-39071) is known. However, this circuit applies to coaxial cables and cannot be applied to single-wire cables. Furthermore, even when applied to coaxial cables, the magnitude of the inductance on the primary and secondary sides of the transformer is the same for both normal high-frequency signals and abnormally large noise. Therefore, if the inductance is too large, a normal high-frequency signal will be attenuated or deteriorated, and the inductance cannot be increased too much. For this reason, this transformer inductance cannot reliably prevent abnormally large noise.

Another improvement is to connect the constant voltage element of the two-way thyristor 31 between the communication line (F) and the other communication line (N) as shown in the ISDN line lightning surge protection circuit in Fig. 20. Connect the constant voltage elements of the 3-pole gas tube arrester 33 (hereinafter, 3-pole arrester) between the communication lines (F, N) and the ground, and connect the communication lines (F) on the load (communication device) side from those constant voltage elements. ) And the other communication line (N) are connected to coordination impedances 35a and 35b (Japanese Patent Application Laid-Open No. 2002-354646). The coordination impedances 35a and 35b are the resistance, the ferrite core, and the inductance caused by twisting both communication lines (F, N).

In the circuit shown in Fig. 20, a three-pole capacitor with a capacitance of several pF is used between both communication lines (F, N) and ground to secure 60 dB or more at 160 kHz for ISDN communication. . The arrester starts discharging after a delay of 2 to 6 seconds after the overvoltage is applied, and during the delay, large noise flows to the load.To reduce the large noise, the coordinating impedance 35a And 35b are connected. However, if the impedance of the coordinating impedances 35a and 35b is increased, the noise can be greatly reduced. Since the signal is also attenuated, the impedance cannot be set too high.

In addition, the two communication lines (F, N) in the circuit of Fig. 20 are connected by a two-way thyristor 31. A bidirectional thyristor with a large short-circuit current is needed to absorb (flow) with the IGBT, but a bidirectional thyristor with a large short-circuit current has a relatively low frequency due to its large capacitance of several 100 pF. Can do, but not high frequency communication. In addition, if a two-way thyristor with a small capacitance is used for high-frequency communication, the short-circuit current is small and large noise cannot be absorbed sufficiently.

Accordingly, the present invention has been developed to solve the problem that a conventional communication line noise prevention circuit could not prevent abnormal large noise from flowing to a load without attenuating a normal high-frequency signal. For a high-frequency signal with normal communication, a high-frequency signal can flow with a very small inductance between the constant voltage element in the input section and the load (communication circuit). In some cases, a very large impedance can be generated to reliably prevent noise from flowing to the load, and the capacitance between both communication lines and the capacitance between both communication lines and ground can be reduced. It is an object of the present invention to provide a noise prevention coil circuit that allows a high-frequency signal to flow by reducing the noise. Disclosure of the invention

According to the present invention, the impedance between a communication input section and a communication circuit (load) is extremely small for a normal high-frequency signal, and extremely low for an abnormally large noise. By connecting a coil circuit that is configured to be large, a normal high-frequency signal flows to the load without attenuation, and a noise prevention coil circuit that reliably prevents abnormal large noise from flowing to the load is realized. is there. Brief description of drawings FIG. 1 is a diagram illustrating a noise prevention coil circuit of the present invention connected between a communication input unit and a load.

FIG. 2 is a diagram illustrating a first embodiment of a noise prevention coil circuit. FIG. 3 is a characteristic diagram of the noise prevention coil circuit of FIG.

FIG. 4 is a diagram for explaining a second embodiment of the noise prevention coil circuit. FIG. 5 is a diagram for explaining a third embodiment of the noise prevention coil circuit. FIG. 6 is a diagram illustrating a fourth embodiment of the noise prevention coil circuit. FIG. 7 is a diagram for explaining a fifth embodiment of the noise prevention coil circuit. FIG. 8 is a diagram for explaining a sixth embodiment of the noise prevention coil circuit. FIG. 9 is a diagram for explaining a seventh embodiment of the noise prevention coil circuit. FIG. 10 is a diagram for explaining an eighth embodiment of the noise prevention coil circuit. FIG. 11 is a diagram for explaining a ninth embodiment of a noise prevention coil circuit. FIG. 12 is a diagram for explaining a differential mode unit according to the ninth embodiment.

FIG. 13 is a characteristic diagram of the noise prevention coil circuit of FIG.

FIG. 14 is a voltage-current characteristic diagram when noise is applied to the noise prevention coil circuit of FIG.

FIG. 15 is a diagram for explaining another circuit of the noise prevention coil circuit of FIG.

FIG. 16 is a diagram for explaining a common mode unit of the ninth embodiment.

FIG. 17 is a voltage-current characteristic diagram when noise is applied to the noise prevention coil circuit of FIG.

FIG. 18 is a diagram for explaining a tenth embodiment of the noise prevention coil circuit. FIG. 19 is a diagram illustrating a first lightning protection circuit of a conventional example.

FIG. 20 is a diagram illustrating a second lightning protection circuit of the conventional example. BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below in detail with reference to the drawings.

Fig. 1 shows the connection of the noise prevention coil circuit of the present invention between the communication input section (terminal H) and the communication circuit (terminal S, load side). E, V is the voltage between terminals H and S of the coil circuit, and r is the internal resistance of the load. Connect a constant voltage element in parallel with the power supply.

FIG. 1 illustrates the magnitude of the impedance of the noise prevention coil circuit of the present invention with respect to a normal high-frequency signal.

As an index of the magnitude of the impedance of the coil circuit when a high-frequency signal flows, the ratio (VZE) of the signal AC voltage E to the voltage V between the terminals HS can be taken. That is, when the internal resistance of the coil circuit becomes so large that it cannot be ignored compared to the internal resistance r of the load, a large voltage is generated between the terminals HS and V / E increases. There is no clear criterion that the value of VZE is negligible below, but in general, when V "E = 0.1, the impedance of the coil circuit is within the allowable range. If / E> 0.1, the signal attenuation in the coil circuit increases, which is not preferable.

The noise prevention coil circuit of the present invention has a small impedance with respect to a normal high-frequency signal, and the ratio of the AC voltage E of the signal to the voltage V between the terminals HS becomes VZE <= 0.1, resulting in abnormally large noise. On the other hand, the coil circuit has a very high impedance and can reliably prevent noise from flowing to the load.

FIG. 2 shows a first embodiment of a noise prevention coil circuit according to the present invention, which is a coil circuit in which a capacitor C1 is connected in parallel to a coil L1. Terminal H is the input side and terminal S is the load side. The inductance of the coil L1 is large enough to prevent large noise flowing into the input terminal H. Now, replace the LC parallel circuit in Fig. 2 with the coil circuit in Fig. 1, and let the inductance of coil L1 be L = 5 mH and the load internal resistance Γ = 200 Ω. Table 1 shows the magnitude of V / E with respect to the frequency f of the input high-frequency signal and the capacitance C of the capacitor C1. If the capacitance C1 of the capacitor C1 is 100 pF, V / E = 0.1 is obtained when the signal frequency f> about 5 OMHz. When the capacitance C1 of the capacitor C1 is 1 nF, VZE <= 0.1 is obtained when the signal frequency f> about 5 MHz. The inductance L = 5 mH of the coil L1 is an example, and the value of the inductance of the coil, the capacitance of the capacitor and the frequency of the signal are not limited to the above, but may be adjusted according to the use conditions, the mounting location, etc. adjust. Therefore, the inductance L1 of the inductance required to prevent the large noise flowing into the input terminal H has the ratio of the signal AC voltage E to the input high-frequency signal IS and the voltage V between the terminals HS equal to VZE. By connecting the capacitor C1 having a capacitance C satisfying <= 0.1 in parallel, the high-frequency signal IS can be supplied to the load without greatly attenuating.

As shown in Table 1, by increasing the capacitance C of the capacitor C1 for a low-frequency input signal, the ratio of the AC voltage E of the signal to the voltage V between the terminals HS becomes V / E = 0. However, if the capacitance C of the capacitor increases, the noise of 100 000 kHz, such as thunder noise and spark noise, and the noise of several hundred kHz can easily flow. Capacity C cannot be too large. The upper limit of the size of the capacitance C of the capacitor C1 is preferably such that the ratio of the signal alternating voltage E to the voltage V between the terminals HS is V / E> 0.5 with respect to abnormal noise. Fig. 3 shows how a normal high-frequency signal flows through coil L1 and capacitor C1. A constant current I L1 of the DC component of the high-frequency signal IS flows through the coil L1, and an amplitude current I C1 of the AC component flows as a charge / discharge current through the capacitor C1. Then, the high-frequency signal IS flows from the output terminal S to the load.

When a large noise flows into the input terminal H, the capacitance of the capacitor C 1 is small enough to allow the amplitude current of the alternating current of the high-frequency signal to flow. However, in response to a sudden current change (increase) due to large noise, the coil L1 functions as a large inductance and generates a large impedance, so it is necessary to ensure that large noise flows to the load. Can be prevented.

By changing the coil L1 to a variable inductance type and the capacitor C1 to a variable capacitance type, it is possible to adjust the noise prevention coil circuit in the optimum state according to the place of use, use conditions, and abnormal conditions. The variable method can be a serial method (changing the value of the series) or a parallel method (changing the value of the parallel), and can be manual or automatic.

Similarly, a square-wave high-frequency signal IS can be passed by selecting the capacitance of the capacitor according to the square-wave high-frequency signal IS.

【table 1】

FIG. 4 shows a second embodiment of the coil circuit of the present invention, which is a coil circuit in which a coil L5 is connected in series to a parallel circuit of the coil L1 and the capacitor C1 in FIG. Terminal H is the input side and terminal S is the load side. Coils L 1 and L 5 are not magnetically sensitive.

In the input signal IS, if the ratio between the signal AC voltage E and the voltage V of the parallel circuit of the coil L1 and the capacitor C1 is V / E> 0.1, the parallel connection of the coil L1 and the capacitor C1 By connecting the coil L5 in series to the circuit and causing the capacitor C1 and the coil L5 to resonate in series, the impedance of the entire coil circuit can be reduced.

As an example, if the inductance of the capacitor L 1 is L = 5 mH, the capacitance of the capacitor C 1 is C = I n F, the load internal resistance is r = 200 Ω, and the frequency of the input signal f = 2 MHz, Table 1 shows that VZE- 0.2. Now, assuming that the inductance of coil L5 is L-6 μΗ, the voltage in the parallel circuit of coil L1 and capacitor C1 and the voltage in coil L5 are in opposite phases, and these voltages are almost equal. And equivalently, the entire coil circuit is short-circuited, resulting in V / E-0.02. This allows the coil circuit to flow the load without attenuating the high-frequency signal IS and without shifting the phase.

By varying the inductance of the coil L5, the phase can be varied, the phase can be adjusted according to the required progress of the phase, and the impedance of the entire coil circuit can be reduced according to the frequency of the high-frequency signal, or , It can be adjusted to the required value.

When a large noise flows into the input terminal H, the coil L1 reliably prevents the large noise from flowing to the load, as in the first embodiment.

FIG. 5 shows a coil circuit according to a third embodiment of the present invention, in which a series circuit of a coil L3 and a capacitor C3 is connected in parallel to a coil L2. Terminal H is the input side and terminal S is the load side. The coils L2 and L3 are magnetically coupled starting from the input terminal H side (black circle).

The coil L2 has an inductance large enough to prevent a large noise flowing into the input terminal H. Since the coil L2 and the coil L3 have the same winding start and are magnetically coupled, the alternating current of the current IL2 flowing through the coil L2 allows the high-frequency signal IS to flow to the load and to charge the capacitor C3. In accordance with the discharge, the coil L 3 and the capacitor C 3 flow as current IC 3 and circulate.Therefore, by selecting the capacity of the capacitor according to the combination of the high-frequency signal IS and the inductance of the coils L 2 and L 3, the input terminal The inductance between H and the output terminal S becomes equivalently small, and the high-frequency signal IS can flow.

As an example, if the inductance of coils L2 and L3 is L2 = 5mH, L3 = 500μΗ, capacitance of capacitor C3 C = 3nF, load internal resistance r = 200Ω, frequency of input signal If f = 2 OMHz, V / E = 0.03.

When a large noise flows into the input terminal H, the capacitance of the capacitor C3 is small enough to flow the high-frequency signal current by the combination of the coils L2 and L3. However, the coil L2 functions as a large inductance, and a large impedance is generated when a sudden current change due to a large noise occurs. Can be reliably prevented. Further, the coil L 3 also serves to suppress the inrush current from flowing through the capacitor C 3 in the event of an abnormality.

When the coil L2 prevents noise, a large reverse voltage is generated in the coil L2.However, the inductance of the coils L2 and L3 is also large in the coil L3 magnetically coupled to the coil L2. Therefore, only the voltage of the difference between the voltage of the coil L2 and the voltage of the coil L3 is applied to the capacitor C3. Therefore, the coil L3 can prevent a large voltage from being applied to the capacitor C3.

FIG. 6 shows a fourth embodiment of the coil circuit of the present invention. The coil circuit of the third embodiment has a coil L2 and a series circuit of a coil L3 and a capacitor C3 connected in parallel. And a coil circuit in which a coil L5 is connected in series. Terminal H is the input side, and terminal S is the load side. Coils L2 and L3 are magnetically coupled, and coils L2, L3 and L5 are not magnetically coupled.

As in the second embodiment, this coil circuit is connected to coil L2 by selecting the inductance of coil L5 in accordance with the equivalent inductance in the coil circuit of coils L2 and L3 and capacitor C2. The voltage in the circuit of L3 and capacitor C3 and the voltage in coil L5 are in opposite phases, and these voltages are almost equal, equivalently, the whole coil circuit is short-circuited. This allows the coil circuit to flow to the load without attenuating the high-frequency signal IS and without shifting the phase.

By varying the inductance of the coil L5, the phase can be varied, the phase can be adjusted according to the required progress of the phase, and the impedance of the entire coil circuit can be reduced according to the frequency of the high-frequency signal. Alternatively, it can be adjusted to the required value.

When large noise flows into the input terminal H, the coil L2 reliably prevents large noise from flowing into the load.

FIG. 7 shows a fifth embodiment of the coil circuit of the present invention. The coil of the third embodiment in which a series circuit of a coil L3 and a capacitor C3 is connected in parallel to a coil L2. This is a coil circuit in which two Zener diodes D2 and D3 are connected in series in the reverse direction between the joint of the circuit coil L3 and capacitor C3 and ground. Terminal H is the input side and terminal S is the load side. The coils L2 and L3 are magnetically coupled starting from the input terminal H side. The combination of the coils L2 and L3 and the capacitor C2 is the same as in the third embodiment, and the description of the same function is omitted.

When a large noise flows into the input terminal H, the coil L2 functions as a large inductance to prevent the noise from flowing to the load, but at that time, the voltage at the connection point between the coil L3 and the capacitor C2 is reduced. Ascending, the diode diodes D 2 and D 3 conduct, and current flows from the coil L 3 to the ground. The current flowing to the ground does not flow through the capacitor C3, and therefore flows through the coil L3 from the beginning to the end of the coil. As a result, a voltage is generated in the coil L2 that causes a current to flow from the end of the winding toward the beginning of the winding, and the coil L2 more strongly prevents noise from flowing to the load.

When negative noise is applied to the input terminal H, which drops to a large negative voltage, zener diodes D2 and D3 conduct, and current flows from the zener diodes D2 and D3 to the coil L3. As a result, coil L2 generates a voltage that causes current to flow from the beginning of winding to the end of winding, and coil L2 prevents negative noise from flowing from the load to input terminal H. I do.

FIG. 8 shows a sixth embodiment of the coil circuit of the present invention, in which coil L2 and coil L3 are connected in parallel between terminal H and terminal S, and coil L is connected between terminal H and ground. This is a coil circuit in which two zener diodes D 2 and D 3 connected in series in the opposite direction to 4 are connected in series. Terminal H is the input side and terminal S is the load side. The coils L2, L3, and L4 are magnetically coupled starting from the input terminal H side. The magnitude of the inductance of each of the coils L2, L3 and L4 is determined so that the normal high-frequency signal IS flows accurately, and a large impedance is generated for noise, thus preventing noise. Decide.

As an example, Oite the inductance of the coil L 2, L 3, L 4 , L 2 = 1 50 μ H, L 3 = 1 35 i H, L 4 = 140 / zH, load the internal resistance r = 200 Omega , V / E = 0. Since this coil circuit is composed of only coils, the value of VZE is the same even if the frequency of the signal is changed. When a normal sine wave or square wave high-frequency signal IS is input to the input terminal H, a current circulating from the coil L2 to the coil L3 flows through the coil L2, so that the equivalent inductance of the coil L2 is obtained. Becomes very small, and the high-frequency signal IS flows from the input terminal H to the load.

When a large noise flows into the input terminal H and the voltage at the input terminal H rises due to the noise, the zener diodes D2 and D3 conduct, and a current flows to the ground through the coil L4. When a large current flows through the coil L4, a large reverse voltage is generated in the coil L4, and opposite voltages are generated in the coils L2 and L3 which are magnetically coupled to the coil L4. L3 prevents noise from flowing to the load.

When negative voltage is applied, the voltage at the input terminal H drops to a large negative value, the zener diodes D 2 and D 3 conduct, and the current flows in the opposite direction from the zener diodes D 2 and D 3 to the coil L 4. In addition, coils L2 and L3 prevent negative noise from flowing from the load toward input terminal H.

FIG. 9 shows a seventh embodiment of the coil circuit of the present invention, in which a coil L2 is connected between a terminal H and a terminal S, and a coil L3 and a capacitor C are connected between the terminal H and the ground. This is a coil circuit in which two Zener diodes D 2 and D 3 connected in series in the opposite direction to the parallel circuit 4 are connected in series. Terminal H is the input side and terminal S is the load side. The coils L2 and L3 start winding around the input terminal H side, and the coils L2 and L3 are magnetically coupled. The magnitude of the inductance of each of the coils L2 and L3 is determined so that the normal high-frequency signal I S flows accurately, and a large impedance is generated for noise to prevent noise.

If a normal sine waveform or square wave high-frequency signal IS is input to the input terminal H and a reverse voltage is generated in the coil L2 due to the flow of the normal high-frequency signal IS, a voltage of the same magnitude is also applied to the coil L3. However, as in the first embodiment, the voltage generated in the coil L3 causes a current circulating in the coil L3 and the capacitor C4 to flow, so that the voltage in the coil L3 decreases. Therefore, the equivalent inductance of the coil L2 becomes very small, and the high-frequency signal IS flows from the input terminal H to the load. When large noise flows into the input terminal H, the noise causes the voltage at the input terminal to rise, and when the Zener diodes D 2 and D 3 conduct, no current flows from the capacitor C 4 to ground, but through the coil L 3. Current flows to the ground, a large reverse voltage is generated in coil L3, and a reverse voltage is generated in coil L2, which is magnetically coupled to coil L3, and noise flows through coil L2 to the load To prevent

When the voltage at the input terminal H is negative and the voltage at the input terminal H drops significantly, the Zener diodes D 2 and D 3 conduct, and current flows from the Zener diodes D 2 and D 3 to the coil L 3, so that the coil L 2 prevents negative noise from flowing from the load toward the input terminal H.

FIG. 10 shows an eighth embodiment of the coil circuit according to the present invention, in which a terminal H is used as an input terminal, a terminal S is used as a load-side terminal, and an enhancement-type first terminal is provided between terminals H and S. (Hereinafter referred to as MOS (Ml)), the coil L2 and the second MOS FET (hereinafter referred to as MOS (M2)). Connect the drain of MO S (Ml) to terminal H, connect the start of coil L 2 to the source of MO S (Ml), and connect the source of MO S (M 2) to the end of coil L 2 Then, connect the drain of MOS (M 2) to terminal S. The beginning of winding of coil L3 is connected to the end of winding of coil L2, and two zener diodes D2 and D3 connected in series in reverse direction between the end of winding of coil L3 and ground are connected in series. Connect to. Connect capacitor C 4 in parallel with coil L 3. The coil L2 and the coil L3 have the same winding direction and are magnetically coupled. 2 MO S

(Ml, M2) is the P-type of enhancement. Connect the resistor R2 and the resistor R3 in series between the input terminal H and the ground, and connect the MOST (Ml) and MOS (M2) guts to the connection point of the resistor R2 and the resistor R3. . Under normal conditions, select resistors R2 and R3 so that MOS (M1, M2) is conducting and high-frequency signals flow. The resistance values of resistors R2 and R3 are large.

Since the coil L2 is magnetically coupled with the coil L3 connected in parallel with the capacitor C4, the coil L2 is equivalent to a coil having a very small inductance, and a normal high-frequency signal IS flows to the load. be able to. When a large positive noise flows into the input terminal H, the noise causes the voltage at the input terminal to rise, and when the Zener diodes D 2 and D 3 conduct, the current does not flow through the capacitor C 4 but flows through the coil L 3. As a result, a large reverse voltage is generated in coil L3, and a reverse voltage is generated in coil L2, which is magnetically coupled to coil L3. Is prevented.

Since the gate of MOS (M2) is connected to the input terminal H and the resistor R2, when a large voltage is generated in the coil L2, the voltage of the gate of MOS (M2) rises, Since M2) is in a non-conductive state, MOS (M2) can completely cut off noise while large noise is applied to the input terminal H.

Of course, by detecting the voltage generated in the coil L2 and controlling the gate voltage of the MOS (M2), the MOS (M2) can be turned off.

When a large negative noise flows into the input terminal H, the noise causes the voltage of the input terminal to drop, and when the zener diodes D2 and D3 conduct, the current does not flow through the capacitor C4 but flows through the coil L3. Flow from ground to the input terminal H, a large reverse voltage is generated in the coil L3, and a reverse voltage is generated in the coil L2 which is magnetically coupled to the coil L3. Prevents the load from flowing to input terminal H.

Since the gate of MO S (Ml) is connected to the ground by the resistor R3, when a large voltage in the opposite direction is generated in the coil L2, the voltage of the gate of MO S (Ml) rises, Since (M l) is in a non-conductive state, MOS (Ml) can completely block the noise while a large negative noise is applied to the input terminal H.

Of course, by detecting the voltage generated in the coil L2 and controlling the gate voltage of the MOS (Ml), the MOS (Ml) can be turned off. Further, it can also be constituted by an N-type MOS FET.

FIG. 11 shows a ninth embodiment of the coil circuit according to the present invention. The load connected to the communication line (F) and the communication line (N) is connected to the differential mode noise and the common mode noise. This is a noise prevention coil circuit to protect from non-mode noise. Communication line

Connect a noise prevention coil circuit for differential 'mode noise' and a noise prevention coil circuit for common 'mode noise' between the (F, N) input section and the load (communication equipment). Connect coil L11 and coil L14 in series between the input of the communication line (F) and the load, and connect coil L12 and coil L15 in series between the input of the communication line (N) and the load. . Connect coil L13, resistor R11, parisers 1, 7, 8 and 2-pole arrester 5 and 3-pole arrestor 6 between the communication lines (F, N) between the input section and coils Lll and L12. One end of the coil L13 is connected to the communication line (F), the palister 1 is connected between the other end of the coil L13 and the communication line (N), and a resistor R11 is connected in parallel with the coil L13. A two-pole arrester 5 and a varistor 7 are connected in series between both communication lines (F, N), and both electrodes of a three-pole arrestor 6 are connected to both communication lines (F, N). Connect a parister 8 between the intermediate electrode and the ground. Communication line (F) connection between coil L11 and coil L14 and communication line

In the (N), between the connection point of the coil L12 and the coil L15, connect the paristers 2 and 3 in series, and connect the coil L16 between the connection point of the noriser 2 and the pariser 3 and the ground. The winding direction (start of winding) of each coil is indicated by a black circle. Also, the palisters 7 and 8 are connected to stop the continuation of the arresters 5 and 6 when the noise application is finished.

The coil circuit for differential mode noise of the circuit of the embodiment of FIG. U will be described separately in FIG. 12, and the coil circuit for common mode noise will be separately described in FIG. The circuit shown in Fig. 12 is composed of coils Lll, L12, L13, resistor R11, Pallisters 1, 7 and 2-pole arrester 5. The coils L11, L12, L13 are magnetically coupled to each other. Now, let the signal of ISND communication be current IS. The current IS is a current obtained by overlapping a DC current with an AC current of a signal. ISND communication current IS force S, when the current flows from the input of the communication line (F) through the coil L11 to the load, coil L12, and the input of the communication line (N), the DC current resistance of the coils Lll and L12 is The voltage drop due to the DC current of the current IS is so small that it can be ignored. Due to the inductance of the coils L11 and L12 and the alternating current of the signal, voltage fluctuation of the signal cycle occurs in each of the coils Lll and L12, but the same applies to the coil L13 magnetically coupled to the coils Lll and L12. Voltage fluctuations of the same period occur. Since the resistor R11 is connected in parallel with the coil L13, the voltage fluctuation generated in the coil L13 causes the coil L13 and the resistor R11 to generate an alternating current having a magnitude close to the alternating current of the signal of the current IS. It circulates and flows. The magnitude of the inductance of the coils Lll and L12 is the same. The inductance of the coil L13 is one example, but is twice or more the sum of the inductances of the coils L11 and L12. Of course, the inductance ratio of coils Lll, L12 and L13 can be adjusted according to the protection characteristics of the circuit.

FIG. 13 shows the current I S, the current I L13 of the coil L13, and the current I R11 of the resistor R11. As shown in Fig. 12, the coils L11 and L12 and the coil L13 are magnetically coupled, so that the current I in the coil L13 has the same magnitude as the AC L13 flows and circulates through resistor R11 as current I R11. When the resistance of the resistor R11 is reduced, the magnitude of the voltage fluctuation generated in the resistor R11 by the current IR11 can be reduced. As the magnitude of the voltage fluctuation in the resistor R11 decreases, the voltage fluctuation in the coils L11 and L12 also decreases. Therefore, the magnitude of the inductance of the coils L11 and L12 is determined by the magnitude of the noise to be protected, and the magnitude of the resistor R11 is selected by the magnitude of the alternating current of the signal of the current IS. The voltage drop in the coils L11 and L12 can be reduced.

Next, the case where a large noise is applied between the communication line (F) and the communication line (N) will be described. Fig. 14 shows the characteristics of the voltage-current characteristics of each part. Now, assuming that a rise time of l / xsec, a fall time of 10 μsec, and a noise with a peak value of 1000 V are applied, coils L11 and L12 have large Reverse voltages VL11 and VL12 are generated. At the same time, a voltage VL13 of the same magnitude as the sum of the reverse voltages of coils L11 and L12 is generated in coil L13. Thereafter, when a voltage equal to or higher than the parister voltage is applied to the parister 1, the Norlister 1 conducts, and the current I L13 of the coil L13 and the current I R11 of the resistor R11 flow, so that the voltage VL13 is applied to the coil L13. Since it occurs continuously, the reverse voltage of coils Lll and L12 also occurs continuously. Then, the arrester 5 does not conduct after the application of the continuous reverse voltage 1S noise of the coils Lll and L12. In order to prevent unwanted voltages from being applied to the load, the load should only be subjected to a pariser voltage. Two to six microseconds after noise application, the two-pole arrester 5 conducts, causing a large current IA5 to flow. 两 When the voltage VF—N between the communication lines (F, N) drops to the palister voltage, the coil L The reverse voltages VL11 and VL12 of ll and L12 and the voltage VL13 of the coil L13 become OV. Even if the voltage VF-N between the two communication lines (F, N) drops to the varistor voltage, the current I L13 of the coil L13 flows almost constant until the noise applied voltage drops to the varistor voltage. , Decrease. The current I RU of the resistor R11 stops when the voltage VF-N between the two communication lines (F, N) drops to the varistor voltage. The current IA5 of the two-pole arrester 5 flows until the applied voltage of the noise decreases to the varistor voltage. When the applied voltage of the noise decreases to the varistor voltage, the varistor 7 becomes nonconductive and stops.

Therefore, even if a large noise voltage is applied between the two communication lines, a voltage higher than the par- sistor voltage is not applied to the load, so that the load can be protected from a large noise voltage. The current flowing through the varistor 1 is the current I L13 of the coil L13 and the current I R11 of the resistor R11.The current I L13 is limited by the inductance of the coil L13, and the current I R11 is Since it is limited by the resistance of 11, the current of the two-pole arrestor 5 is 1 / several tens of the current I A5, so the varistor 1 can use a varistor with small surge current capacity and small capacitance. .

The arrester starts discharging 2 to 6 µs after the overvoltage is applied, but some arresters start discharging 10 µs or more later. Even if the discharge of the arrester 5 is delayed by 10 μsec or more, a voltage higher than the varistor voltage is applied to the varistor 1 until the arrester 5 discharges, the current IL 13 continues to flow through the coil L 13, and Since the reverse voltage occurs continuously, only the varistor voltage is applied to the load.

As shown in the circuit of FIG. 15, when one communication line (N) of the circuit of FIG. 12 is connected to the ground, the coil L12 of the communication line (N) can be removed. In other respects, the circuit is the same as that of the circuit in FIG. 12, so that a large noise can be prevented without applying a voltage higher than the parister voltage to the load. In this case, the magnitude of the inductance of the coil L13 is, as one example, that of the coil L11. It is the same size or close to it. Of course, the ratio of the inductance of the coils L11 and L13 can be adjusted according to the protection characteristics of the circuit.

Next, the circuit in FIG. 16 for common mode noise consists of coils L14, L15, L16, paristers 2, 3, 8 and a three-pole arrester 6. The coils L14, L15, L16 are magnetically coupled to each other. Since the coils L14 and L15 are for the common mode, the voltage drop (fluctuation) in the coils L14 and L15 due to the alternating current of the signal current IS of the ISND communication is very small and negligible. Therefore, a case where a large common 'mode noise is applied between both communication lines (F, N) and ground will be described. The characteristics of the voltage-current characteristics of each part are shown in FIG. Assuming that noise with a rise time of 1 / xsec, a fall time of 10 μsec, and a peak value of 1000 V is applied, a large reverse voltage VL14 is applied to the coils L14 and L15 in response to a sudden current change. , And VL15 occur. At the same time, a voltage VL16 of the same magnitude as the reverse voltage of the coils L14 and L15 is generated in the coil L16. After that, when a voltage higher than the parister voltage is applied to the paristers 2 and 3, the nolisters 2 and 3 conduct, and the current I L16 of the coil L16 flows, so that the voltage VL16 is continuously generated in the coil L16. In addition, the reverse voltage of the coils L14 and L15 also continuously occurs. Then, the continuous reverse voltage of the coils L14 and L15 is applied between the load and the ground to prevent a large voltage from being applied to the load for 2 to 6 / xsec during which the 3-pole arrester 6 does not conduct after the application of noise. Applies only the parister voltage. Two to six microseconds after noise is applied, the three-pole arrester 6 conducts, a large current IA6 flows, and the voltage VFN-G between both communication lines (F, N) and the ground drops to the parister voltage. Reverse voltage VL14, VL15 of coil L14, L15 and voltage VL16 of coil L16 become 0V. Even if the voltage VFN-G between the two communication lines (F, N) and the ground drops to the parister voltage, the current I L16 of the coil L16 is almost constant until the noise applied voltage drops to the parister voltage. Flows and then decreases. The current IA6 of the three-pole arrester 6 flows until the applied voltage of the noise decreases to the varistor voltage, and when the applied voltage of the noise decreases to the varistor voltage, the varistor 8 becomes nonconductive and stops. The magnitude of the inductance of the coil L16 is, for example, the same as or close to that of the coils L14 and L15. of course, The ratio of inductors and chairs in coils L14, L15 and L13 can be adjusted according to the protection characteristics of the circuit.

Therefore, even if a large noise voltage is applied between the two communication lines and the ground, a voltage higher than the parister voltage is not applied between the load and the ground, so that the load can be protected from a large noise voltage. In addition, the current flowing through the paristers 2 and 3 is the current I L16 of the coil L16, but since the current I L16 is limited by the inductance of the coil L16, the 1 Z number of the current IA 6 of the three-pole arrester 6 Since the current is as small as 10, the varistors 2 and 3 can use varistors with small surge current resistance and small capacitance.

In Fig. 18, coil L17 is connected between the input of communication line (F) and the load, and coil L19 is connected between the input of communication line (N) and the load. A varistor 9, a coil L18, a coil L20, and a varistor 10 are connected in series between both communication lines (F, N) between the input section and the coils L17, L19. A resistor R12 is connected in parallel with 20, and a pariser 11 is connected between the connection point of coil L18 and coil L20 and the ground. A two-pole arrester 5 and a palister 7 are connected in series between both communication lines (F, N), and both electrodes of a three-pole arrester 6 are connected to both communication lines (F, N). Connect a resistor 8 between the electrode and ground. The coils L17 and L18 are magnetically coupled to each other, and the coils L19 and L20 are magnetically coupled to each other. The winding direction of each coil is indicated by a black circle. Paristers 7 and 8 are connected to stop the continuation of arresters 5 and 6 when the noise application ends.

In the circuit of Fig. 18, when the signal current IS of the ISDN communication flows from the input of the communication line (F) through the coil L17 to the load, coil L19, and the input of the communication line (N), As with the circuit, the DC current resistance of the coils L17 and L19 is very small, several tens of milliohms, so the voltage drop due to the DC current of the current IS is negligibly small. Due to the inductance of the coils L17 and L19 and the alternating current of the signal, a voltage fluctuation of the signal cycle occurs in each of the coils L17 and L19.The coil L18 magnetically coupled to the coil L17 also includes the coil L19. A voltage fluctuation of the same period and the same magnitude also occurs in the coil L20 magnetically coupled to the coil L20. Since the resistor R12 is connected in parallel with the coil L18 and coil L20 connected in series, Due to the voltage fluctuations generated at 18 and L20, an alternating current of a magnitude close to the alternating current of the current IS signal flows through the coils L18 and L20 and the resistor R12. The magnitudes of the inductances of the coils L17 and L19 are the same. The inductance of the coils L18 and L20 is one example, but is equal to or close to the magnitude of the inductance of the coils L17 and L19. Of course, the ratio of the inductance of the coils L17, L19 and L18, L20 can be adjusted according to the protection characteristics of the circuit.

Next, the case where large noise in the differential mode is applied between the communication line (F) and the communication line (N) will be described. Now, assuming that the rise time l ^ sec ^ the number of fall times is ΙΟμsec and the noise with a peak value of 1000 V is applied, the coils L17 and L19 have a large reverse voltage due to a sudden current change. Pressure develops. At the same time, a voltage having the same magnitude and the same direction as the reverse voltage of the coil L17 is generated in the coil L18, and a voltage having the same magnitude and the same direction as the reverse voltage of the coil L19 is generated in the coil L20. After that, when a voltage higher than the varistor voltage is applied to the varistors 9 and 10, the noristers 9 and 10 conduct, and current flows through the coils L18 and L20 and the resistor R12, so that the voltage continues to the coils L18 and L20. Therefore, the reverse voltage of the coils L17 and L19 also continuously occurs. In order to prevent the continuous reverse voltage of coils L17 and L20 from applying a large voltage to the load during 2 to 6 μ3θθ when the arrester 5 does not conduct after noise is applied, the load must be Only voltage is applied. Two to six microseconds after noise application, the two-pole arrester 5 conducts, causing a large current IA5 to flow, and when the voltage VF-N between the two communication lines (F, N) drops to the parister voltage, the coil The reverse voltage of L17 and L19 and the voltage of coils L18 and L20 become OV. Even if the voltage VF-N between the two communication lines (F, N) drops to the varistor voltage, the current in the coils L18 and L20 flows almost constant until the noise applied voltage drops to the palister voltage. , Decrease. The current of the resistor R12 stops when the voltage VF-N between both communication lines (F, N) falls to the varistor voltage. The current IA5 of the two-pole arrester 5 flows until the applied voltage of the noise drops to the varistor voltage, and when the applied voltage of the noise drops to the varistor voltage, the varistor 7 becomes nonconductive and stops. This section describes the case where large common-mode noise is applied between both communication lines (F, N) and ground. Now, assuming that a rise time l wse a fall time of several seconds and a noise with a peak value of 1000 V are applied, a large reverse voltage is generated in the coils L17 and L19 in response to a sudden current change. At the same time, a voltage of the same magnitude and the same direction as the reverse voltage of the coil L17 is generated in the coil L18, and a voltage of the same magnitude and the same direction as the reverse voltage of the coil L19 is generated in the coil L20. . After that, when a voltage higher than the varistor voltage is applied to the varistors 9, 10, and 11, the varistors 9, 10, and 11 conduct, and pass through the varistor 9 and the coil L18 to the varistor 11, and the varistor 10 and the coil When a current flows through the parister 11 through L20, a voltage is continuously generated in the coils L18 and L20, so that a reverse voltage of the coils L17 and L19 is also continuously generated.

Then, the continuous reverse voltage of the coils L17 and L19 is applied between the load and the ground to prevent large voltage from being applied to the load for 2 to 6 / sec when the 3-pole arrester 6 does not conduct after the noise is applied. Only applies a parister voltage. After 2 to 6 / zsec of noise application, the three-pole arrester 6 conducts, a large current I A6 flows, and the voltage V FN— G between both communication lines (F, N) and the ground drops to the varistor voltage. The reverse voltage of the coils L17 and L19 and the voltage of the coils L18 and L20 become 0 V. Even if the voltage between both communication lines (F, N) and ground VFN-G drops to the varistor voltage, the current of coils L18 and L20 is almost constant until the noise applied voltage drops to the varistor voltage. Flow, and then decrease. The current IA 6 of the three-pole arrester 6 flows until the applied voltage of the noise decreases to the varistor voltage, and when the applied voltage of the noise decreases to the varistor voltage, the varistor 8 becomes nonconductive and stops. Further, the varistor voltage of the nolisters 9, 10, and 11 is 1Z2 of the varistor voltage of the varistors 7 and 8.

Therefore, even if a large noise voltage is applied between the communication lines, the load is not applied with a voltage higher than the parister voltage, so that the load can be protected from a large noise voltage. Even if a large noise voltage is applied, a voltage higher than the pariser voltage is not applied between the load and the ground, so that the load can be protected from a large noise voltage. The current flowing through the varistors 9, 10, and 11 is the current of the coils L18 and L20, but the inductance of the coils L18 and L20. Is smaller than the current I A5 of the two-pole arrestor 5 and the current IA6 of the three-pole arrestor 6 by 1 / several tens. A parister having a small capacitance can be used. By combining the circuits for mode and common mode, the capacitance between both communication lines and the capacitance between both communication lines and ground can be reduced to 20 pF, 1 O pF, or less. It can be used for ISDN communication, ADSL communication, and higher speed communication. It is self-evident that the nolister can be replaced by an avalanche diode or a thyristor (PNPN element) if necessary. Industrial applicability

As described above, the noise prevention circuit of the present invention can transmit a normal high-frequency signal and can reliably prevent a large noise. It can be used for equipment. In addition, this noise prevention coil circuit can protect (cut off) lightning surge and harmonic noise in AC and DC power supply lines of commercial power supply, and can be used to protect a wide range of power equipment.

Claims

The scope of the claims

1.In a coil circuit connected between the communication input section and the communication circuit, for a normal high-frequency signal, the ratio between the signal AC voltage E and the voltage V in the coil circuit is V / E = 0. A noise prevention coil circuit that has a small impedance of 1 and has a very large impedance of V / E> 0.5 for abnormally large noise.

2. The noise prevention coil circuit according to claim 1, wherein a capacitor (C 1) is connected in parallel to the coil (L 1).

3. The noise prevention coil circuit according to claim 1, wherein a capacitor (C 1) is connected in parallel to the variable coil (L 1).

4. The noise prevention coil circuit according to claim 1, wherein a variable capacitor (C1) is connected in parallel to the coil (L1).

5. The noise prevention coil circuit according to claim 1, wherein a variable capacitor (C1) is connected in parallel to the variable coil (L1).

6. The noise according to claim 1, wherein a coil (L5) that generates a voltage substantially equal to the voltage of the parallel circuit in an opposite phase is connected in series to a parallel circuit of the coil (L1) and the capacitor (C1). Prevention coil circuit.

7. The variable coil (L5) for generating a voltage substantially equal to the voltage of the parallel circuit in the opposite phase to the parallel circuit of the coil (L1) and the capacitor (C1) is connected in series to the parallel circuit of the coil (L1) and the capacitor (C1). Noise prevention coil circuit.

8. A series circuit of a coil (L3) and a capacitor (C3) is connected in parallel to the coil (L2), and the coils (L2, L3) are magnetically coupled with the same winding start. The noise prevention coil circuit according to claim 1.

9. A series circuit of a coil (L3) and a capacitor (C3) is connected in parallel to the coil (L2), and the coils (L2, L3) are magnetically coupled with the same winding start. The noise prevention coil circuit according to claim 1, wherein a coil (L5) is connected in series to the circuit.

10 0. A series circuit of a coil (L 3) and a capacitor (C 3) is connected in parallel to the coil (L 2), and the coils (L 2 and L 3) are magnetically coupled with the same winding start. The coil (L 3) and the capacitor (C 3) 2. The noise prevention coil circuit according to claim 1, wherein two Zener diodes (D2, D3) are connected in series in opposite directions between the connection point of (1) and the ground.

1. In the coil circuit connected between the communication input section and the communication circuit, connect the coil (L2) and the coil (L3) in parallel between the input terminal and the communication circuit, and connect between the input terminal and the ground. A coil (L 4) and two zener diodes (D 2, D 3) connected in series in the opposite direction are connected in series, and the coils (L 2, L 3, L 4) have the same winding start, 2. The noise prevention coil circuit according to claim 1, wherein the coil circuit is magnetically coupled.

2. In the coil circuit connected between the communication input section and the communication circuit, connect the coil (L2) between the input terminal and the communication circuit, and connect the coil (L3) and capacitor ( The parallel circuit of C 4) and two Zener diodes (D 2, D 3) connected in reverse series are connected in series, and the coil (L 2 "L 3) is magnetically coupled with the same winding start. The noise prevention coil circuit according to claim 1.

3. Connect the drain of the enhancement-type first MOSFET to the communication input terminal, connect the start of winding of the coil (L2) to the source of the first MOSFET, and connect the coil (L At the end of the winding of 2), the source of the enhancement type second MOSFET is connected, the drain of the second MOS FET is connected to the communication circuit, and the winding of the coil (L3) is started. Is connected to the end of the winding of the coil (L 2), and two Zener diodes (D 2, D 3) are connected in series in the reverse direction between the end of the winding of the coil (L 3) and the ground; A capacitor (C 4) is connected in parallel with the coil (L 3).

(L2, L3) are magnetically coupled, a resistor (R2) and a resistor (R3) are connected in series between the communication input terminal and the ground, and the gate of the first MOS FET and the 2. The noise prevention coil circuit according to claim 1, wherein a gate of the second MOSFET is connected to a connection point between the resistor (R 2) and the resistor (R 3).

4. Connect the coil (L11) between the input of the communication line (F) and the load, and connect the coil (L12) between the input of the communication line (N) and the load.

N), connect a coil (L13) and a parister (1) between the input A resistor (R11) is connected in parallel with the coil (L13), and a two-pole arrester (5) and a pariser (7) are connected in series between the inputs of both communication lines (F, N). (Lll, L12, L13) are coupled magnetically to the differential mode noise circuit, and the coil (L14) is connected between the input of the communication line (F) and the load, and the communication line (N) A coil (L15) is connected between the input section and the load, and a pariser (2) and a pariser (3) are connected in series. A connection is made between the pariser (2) and the pariser (3) connection point and ground. Connect the coil (L16), connect the electrodes at both ends of the three-pole arrester (6) between the inputs of both communication lines (F, N), and connect the ground between the intermediate electrode of the three-pole arrester (6) and the ground. A varistor (8) is connected to the coil, and a common mode noise circuit in which the coils (L14, L15, L16) are magnetically coupled is connected in series. Prevention coil circuit.

5. The magnitude of the inductance of the coil (L13) is twice or close to the sum of the magnitudes of the inductances of the coils (Lll, L12). 15. The noise prevention coil circuit according to claim 14, wherein the size is equal to or close to the size of the coils (L14, L15).

6. Connect the coil (L11) between the input of the communication line (F) and the load, and connect the coil (L13) and the varistor (1) in series between the input of the communication line (F) and the ground. The differential circuit according to claim 14, wherein a resistor (R11) is connected in parallel with the coil (L13), and a two-pole arrester (5) and a palister (7) are connected in series between the communication line (F) and the ground. Rental モード A noise prevention coil circuit for mode noise.

7. Connect a coil (L17) between the input part of the communication line (F) and the load, and connect a coil (L19) between the input part and the load of the communication line (N). Between the two communication lines (F, N) between L and L 19), a series connection of a nolister (9), a coil (L18), a coil (L20) and a palister (10) is made. A resistor (R12) is connected in parallel to the coil (L18, L20), and a varistor (11) is connected between the connection point between the coil (L18) and the coil (L20) and ground, and both communication lines ( F, N) between the two-pole arrester (5) and Paris (7) are connected in series. (4) Connect both ends of the three-pole arrester (6) to the communication lines (F, N), and connect a parister ( 8), wherein the coils (L17, L18) are magnetically coupled, and the coils (L19, L20) are magnetically coupled.